Kasai-Osaki Uprising

The Kasai-Osaki Uprising was a peasant rebellion in 1591 by Date retainers loyal to Masamune Date, who fought against the Toyotomi, who took away their lands. The rebellion did well at first, but Concubine Kai crushed it.

Background
By 1590, Hideyoshi Hashiba's Toyotomi clan had taken over all of Japan and had founded the Toyotomi Shogunate. He took over the land by taking Odawara from the stubborn Hojo clan. Masamune Date, a daimyo forced to submit to the Toyotomi, refused to take part in the Siege of Odawara, and his lands were taken away. However, his people also were stripped of their lands and belongings, and the Date retainers Harunobu Kasai and Yoshitaka Osaki rebelled in Miyagi Province. Masamune sent equipment to the rebels, including rifles, but did not directly take part in the battle.

Battle
Concubine Kai and an army of Toyotomi Army troops invaded Miyagi, hoping to suppress the rioting before a rebellion broke out. The rebels surrounded her father, Ujinaga Narita, who was in command of a unit of government troops. Kai rescued him before rendezvousing with Nagachika Narita, brother to Ujinaga. Soon, Yukimura Sanada arrived as Toyotomi reinforcements, and the rebels faced a great threat. Harunobu Kasai and Yoshitaka Osaki were slain in the uprising by the government troops, who slowly closed in on the rebels. Ujifusa Hojo was defeated, but Kai slew his attackers.

Kai became suspicious of Masamune's part in the rebellion when his lieutenant Magoichi Saika arrived with Magoroku Saika, two of Masamune's trusted commanders. Concubine Kai and Kunoichi Sanada slew Magoroku and forced Magoichi to surrender. Soon, after slaying Kojiro Katakura, the gates of Miyagi Castle opened, and Masamune Date was found there. He was arrested, but proved his innocence after showing Hideyoshi a letter bearing a call to arms from "Masamune Date", and proved it fake by showing that the stamp was incorrect and not his signature. The uprising was quelled, and Masamune submitted.